This invention relates generally to pumps used for fighting fire, and more particularly, to automatically controlling pumps connected in tandem and/or parallel-tandem configurations.
Fire fighting pumps are important in the forestry industry, as well as in other applications. For example, water is not always readily available in the forest where it is needed to fight a fire. At times, water may be pumped thousands of feet through varying terrains and elevations to get to the fire. The water also needs to be delivered with a desired flow rate capacity.
Pressure loss is caused, in part, by increases in elevation, also referred to as “static head”. Typically, for every one foot of elevation there is a loss of approximately 0.5 pounds per square inch (psi), and static head is the difference in elevation between the pump discharge outlet and the nozzle at the end of the hose. For example, if the pump being used produces 100 psi and an elevation difference of 100 feet exists between the pump and the nozzle end of the hose, only 50 psi is available at the nozzle. Friction loss is a loss of pressure due to friction between the water and the hose. The friction loss increases as the flow in the hose increases.
A higher pressure pump may be used to overcome some pressure and friction losses. A single pump with very high pressure, however, is often not a viable solution due to the pressure rating limitations of the hose. If the pump produces too much pressure, there is a chance that the hose will burst. Therefore, pumps are often set up in tandem, or in series with one another, with one pump pumping water to the next pump and so on, to create a water supply line. The distance between pumps varies depending on the terrain, elevation and equipment being used. Generally, pumps may be located 500 feet to 1000 feet apart.
It is difficult for a single operator to control each pump in a water supply line due to the terrain and the distance between the pumps. Typically, two operators are needed to start and stop the pumps connected in tandem. If a single operator is available, the operator starts one pump, moves to the next downstream pump to start it, and so on. If one pump stops unexpectedly or the water supply is disconnected, the operator needs to run between pumps to turn them on and off as needed, as it is undesirable for a pump to run dry as it may sustain damage as well as waste fuel and water.
Therefore, a need exists for a system to simultaneously control pumps operating in tandem. Certain embodiments of the present invention are intended to meet these needs and other objectives that will become apparent from the description and drawings set forth below.